Manufacturers of products that are produced in high volume as part of a process using, for example, a process line, employ quality assurance methods to ensure that certain features of the product (e.g., color, pattern, alignment, texture) are consistent and match a production reference standard. The product moving down a process line is often spatially oriented in a random manner along the process line. For example, soda cans having a specific pattern printed on the cylindrical outer surface are typically oriented randomly about the vertical axis of rotation of the predominantly cylindrical can. Examples of such processes include package printing processes, soda can printing processes, soda can filling processes, and other processes which may employ more complex color schemes that are repeated or are placed next to each other in use.
A challenging task is to detect and eliminate so called “rogue” cans from the processing line. A rogue can is a soda can that gets onto the processing line accidentally. For example, soda cans from a previous run (e.g., a sugar-free soda product run) get squirreled away in some corner of the conveyor of the processing line and then pop out on the line during a current run (e.g., a sugar-based product run). If such a rogue can is not detected, a sugar-free labeled soda can will be filled with a sugar-based soda product. This could be devastating to, for example, a diabetic person who drinks the sugar-based product from the sugar-free labeled soda can. In general, a “rogue” can or object is an object whose exterior printing or labeling is significantly different from that of the current product running on the processing line. “Significantly different” usually means that the rogue object is for another product altogether (e.g., for a sugar-free soda product instead of a sugar-based soda product).
Rogue cans tend to occur infrequently (e.g., one out of every million cans) and, in general, they do not tend to occur in groups. Therefore, to detect rogue cans, every soda can on the processing line must be observed. It is not sufficient to periodically sample the soda cans as they come down the processing line. Another type of rogue can is called a “silver bullet”. A silver bullet is a soda can that has not been printed (i.e., the outside of the can remains its original silver color). Soda cans may occasionally somehow sneak through the printing process without being printed. Silver bullets do tend to come down the processing line several at a time, however. This can occur, for example, when a printing process is running low on printing ink and switches in a new container of ink. Several soda cans may get past the printing step as silver bullets while the new container of ink is being switched in to be used.
Therefore there remains a need in the art for a fast and convenient way to efficiently monitor a production process with respect to detect so called “rogue objects” (e.g., “rogue soda cans”), where the production objects being monitored may have a random spatial orientation, at least around one axis.
Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such systems and methods with the present invention as set forth in the remainder of the present application with reference to the drawings.